1. Field of the Invention
The present invention relates to a power output apparatus, a hybrid vehicle, and control methods of the power output apparatus and the hybrid vehicle.
2. Description of the Prior Art
One proposed power output apparatus changes the idle rotation speed of an engine as an output source of driving force according to the residual charge level or current state of charge and the temperature of a battery (see, for example, Japanese Patent Laid-Open Gazette No. 2003-206777). This prior art power output apparatus increases the idle rotation speed of the engine, when the residual charge level of the battery decreases to or below a preset reference value corresponding to the battery temperature. The increase of the idle rotation speed of the engine protects the battery from over discharge and accordingly prevents accelerated deterioration of the battery.